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Mediterranean fluvial hydrology is characterised by decadal-to-multi-centennial length wet and dry episodes with abrupt transitions related to changes in atmospheric circulation. Since the mid-1990s site-based flood chronologies from slackwater deposits in bedrock rivers and regionally aggregated flood histories from alluvial deposits have developed increasingly higher resolution chronological frameworks, although regional coverage is still uneven. This paper analyses the spatial and temporal distribution of extreme Holocene hydrological events recorded in fluvial stratigraphy in the Iberian Peninsula (Spain and Portugal), southern France, southern Italy, Northern Africa (Morocco and Tunisia) and eastern Mediterranean (Greece, Crete, Turkey, Cyprus and Israel). This study constitutes the most comprehensive investigation of Holocene river flooding ever undertaken in the Mediterranean and is based on the analysis of 515 14 C and 53 OSL dates. It reveals that flood periods in different regions cluster into distinct time intervals, although region-wide flooding episodes can be identified at 7400–7150, 4800–4600, 4100–3700, 3300–3200, 2850–2750, 2300–2100, 1700–1600, 1500–1400, 950–800, ca. 300, 200–100 cal. BP. Periods with more frequent floods in the western Iberian region coincide with transitions to cool and wetter conditions and persistent negative NAO mode. In Northern Africa increased flood frequency coincides with periods of generally drier climate, while in the eastern Mediterranean there is a higher incidence of extreme flood events under wetter conditions. Our meta-data analysis identifies an out-of-phase pattern of extreme events across the Mediterranean over multi-centennial timescales, which is particularly evident between the western Iberian and eastern Mediterranean regions. This centennial-to-multi-centennial see-saw pattern in flooding indicates that bipolar hydroclimatic conditions existed in the Mediterranean during the Holocene. [ABSTRACT FROM AUTHOR]

Abstract: Two stages of depositional high-discharge fluvial environments are recorded in the infilling of a rock shelter in a canyon of the Segura River, namely: (1) First stage: aggradational alluvial gravels in the lower part, interpreted as braided channel bars (Seventh millennium to 2030calBC), and (2) Second stage: slackwater flood deposits in the upper part (between 2030calBC and after 900AD) during a stage of main channel incision. Reconstructed flood discharges for the second stage were a minimum of 700m3/s. Extreme palaeofloods that inundated the cave from the canyon inlet were successively higher and are correlated to quick-rising flash floods. The characteristics of cultural remains preserved by flood deposits reveal long periods of human cave occupation (and passage through the canyon) without extreme floods occurring. These long periods of low-discharge fluvial flow punctuated by catastrophic flash floods are linked to a torrential fluvial regime. The torrential regime is the current hydrologic and climatic scenario in the streams of semi-arid southeastern Spain. It is discusses the climatic versus anthropogenic factors affecting the fluvial development. We conclude that the archaeo-fluvial record of the Pozo Rock Shelter indicates that the present-day semi-arid conditions of the southeastern Spain drylands extend back to circa 4000yr BP. Methodologically, the combination of fluvial palaeohydrology and geoarchaeology appears to be a robust tool to reconstruct long-term Holocene climate changes. [Copyright &y& Elsevier]

Abstract: The cross-referencing of sedimentological, stratigraphic, geoarchaeological and radiocarbon data enables us to establish the geomorphologic evolution of the Late Holocene coastal flood plain of the Turia River. The Holocene marine transgression formed a coastal barrier lagoon environment in the coastal plain. During the Late Holocene, increased sediments supplied to the low reach of the river promoted: (a): the progradation of deltaic coastal sandy ridges on the coastline and (b): the aggradation of the floodplain on top of the sedimentary sequence. Four phases are clearly recognised in the geoarchaeological record of the flood plain. (1): High magnitude flooding events (2800BP to 3rd century BC). (2): Slow riverbed aggradation and progressive levee formation (low energy flood regime) in Roman times (2nd century BC to 5th century AD). (3): Swampy environmental processes (6th to 9th centuries). (4): Second high-magnitude flooding phase (11th century). The navigable channel of the Roman and early Islamic periods became a wide and shallow braided channel in Medieval times. These phases are correlated with others detected by researchers in many areas of the Mediterranean region and with global Holocene climate events. [Copyright &y& Elsevier]

Abstract: Flooding of rivers in India is linked with the peak monsoons. Investigating the linkage between monsoonal patterns and flood history of various rivers is therefore of fundamental importance in the Indian context. In the present study, the slackwater deposits in the alluvial reaches of the Mahi river basin, western India have been documented. These occur in the ravines incised during the early Holocene on an alluvial surface comprising sediments of Late Pleistocene age. The slackwater deposits occur at elevations up to 20 m from the present river level and extend to about 500 m inland. The carbonate rich sediments forming the ravine cliffs have provided bank stability and the dissections in the ravines have helped in the accumulation of slackwater deposits due to backflooding of the floodwater from the main channel. Recent gullies have incised the sediments and exposed deposits related to major flood events. The best exposures of slackwater deposits have been observed at Dodka. The sediment succession of the slackwater deposits is dominated by bedsets and laminasets of silt and sand separated by colluvial sediments. Four events of flood deposition occurred during the mid to late Holocene. Two units of slackwater deposits, SWD 2 and 4 have been dated by IRSL at 4.6±1 ka and 1.7±0.5 ka. The stratigraphy of these deposits indicates that the first two slackwater units (SWD1 and SWD2) have resulted due to flooding in a regime of intense monsoon. The other two units, however, represent extreme high magnitude floods in a period of low average precipitation. [Copyright &y& Elsevier]